This invention relates generally to the field of dishwasher pumps and more particularly to a pump having an improved cutter system for cutting or comminuting food and miscellaneous particles carried by dishwashing fluid. A cutter constructed in accordance with the teachings of the instant invention is rotatable in two directions add provides a first degree of cutting or comminution in one direction and a second lesser degree of cutting in the opposite direction of rotation.
Several cutter designs for dishwasher pumps and food blenders have been utilized by the appliance industry. One typical cutter is disclosed in U.S. Pat. No. 3,156,278 issued Nov. 10, 1964 to Otto. This patent is directed to a food blender having arcuate blades with a trailing edge in the direction of rotation. The arcuate blades are pivotally connected to a single direction drive shaft. There is no suggestion of a cutter having different operating characteristics in two directions of rotation.
Cushing et al, in U.S. Pat. No. 3,434,671, issued Mar. 25, 1969, teach macerating means for a dishwashing pump having a single blade extending outward along a generally radial line and having a pivotal connection to the drive shaft of the drive motor. The blade includes a cutting edge, is closely spaced from a grid-like grading element at the pump inlet and is operable in a single direction for macerating food particles.
Hahn et al, in U.S. Pat. No. 3,981,456 issued Sept. 21, 1976, and Ziegler, in U.S. Pat. No. 4,201,345 issued May 6, 1980, each disclose a cutter formed from wire and attached to the shaft of the drive motor for rotation thereby. The wire cutter is rotated adjacent a grading element having grid-like openings for effecting the maceration of food particles. Again the cutter rotates in only one direction.
Dingler et al, in U.S. Pat. No. 4,350,306 issued Sept. 21, 1982, teach a combination recirculating and drain pump construction with a soft food disposer having a chopper blade formed to provide turbulent agitation of dishwashing liquid immediately upstream of a filter screen. The blade is formed from a flat sheet and a radially extended arm is twisted about a generally horizontal radial axis to provide a form for effecting the turbulent action.
Meyers, in U.S. Pat. No. 4,448,359 issued May 15, 1984, discloses a dishwasher drain pump which includes an impeller having means for cutting food particles. The impeller has a disc-shaped base with a plurality of soil sizing orifices and an upstanding peripheral rim. At least one breaker tooth extends upwardly from the base and passes by a stationary tooth extending downwardly from a cover plate. Food particles are sheared by the breaker tooth and stationary tooth and pass through the orifices in the base of the impeller prior to being pumped out of the drain cavity. The pump disclosed in this patent is operable in two directions but the cutting action of the drain impeller is the same in both directions of rotation.
The prior art has thus shown a number of different cutters usable with dishwasher pumps to effect comminution of food and other particles carried by the dishwashing liquid. Several of these dishwasher pumping systems are unidirectional for pumping fluid in only one direction and thus there is no concern with the effects of rotating the cutter blade in an opposite direction. The prior bidirectional pumping systems which rotate in one direction for recirculation and in another direction for drain maintain similar cutter operating characteristics in both directions of rotation. It is believed that there has been no showing in the prior art of the proposed dishwasher pump with a food cutter system wherein a vigorous first degree of cutting is provided in one direction of rotation and wherein a second lesser degree of cutting is provided in the opposite direction of rotation.